Three-phase alternating current is widely applied in various fields. Generally, a three-phase alternating current system transmits electricity by using three live lines whose phases differ by 120 degrees, where a neutral wire is optionally included. Phases of the three live lines may be separately referred to as a U phase, a V phase, and a W phase. The phases of a three-phase alternating current may change due to a change of a working environment and/or a malfunction in a circuit, for example, phase loss or phase reversal, thereby causing damage to electrical equipment. Therefore, it is necessary to detect the phases of the three-phase alternating current, in order to ensure that the electrical equipment works in a normal power supply condition.
However, there are too many components in most conventional solutions for three-phase circuit detection, and therefore, the conventional solutions have complex structures, and thus have high costs while poor reliability.